This invention relates generally to pneumatic impact hammers of the type having an impact piston and a fluid delivery tube received within a coaxial bore in the piston for supplying pneumatic pressure fluid to one or both ends of the piston operating chamber for and upon reciprocation of the piston.
U.S. Pat. No. 5,205,363 discloses a conventional hammer and percussion bit assembly having a backhead for mounting an inlet check valve and a mounting hub for mounting a fluid delivery tube. A compression ring or belleville washer is compressed between the backhead and the mounting hub to bias the backhead and mounting hub into engagement with respective snap rings. The snap rings are subject to vibration induced-wear which can lead to failure of the snap rings. In addition, the compression ring/belleville washer was also subject to failure.